Resistor



Nov. 8, 1927. I 1,648,871

G. H. WHITTINGHAM RESISTOR Filed Nov. 29, 1926' Patented Nov. 8, 1927.

UNITED STATES PATENT OFFICE.

GEORGE E. WHI'I'TINGHAM, OF BALTIMORE, MARYLAND, AS SIGNOE TO MONITOBOON- TROLLER COMPANY, OF BALTIMORE, MARYLAND, A CORPORATION OF MARYLAND.

RESISTOR.

Application filed November This invention relates to aresistor comprising a metal supporting bar, a coverlng of refractory material on the bar, of resistance wire wound on said code/ring.

The covering material employed is porcelain, which is desirable because of its refractory nature and high, insulating properties; but as it is impracticable to make long straight pieces of this material, the covering is made in relatively short sections. Where the resistance wire is of very small gage, it is apt to slip into small crevices between the insulator sections, in the winding process, if these sections are made with squared abutting ends, and, to prevent this, I form-each section with an end which is inclined at a much greater pitch with respect to the axis of the supporting-bar than the pitch of the convolutions of the helix, and the inclined end of each section abuts, against the similarly inclined end of another section, so that there are no crevices between the sections running parallel, or nearly par allel with the convolutions of the helix and into which said convolutions might slip. The sections are preferably semi-cylindrical in cross section, grooved on their inner faces to interlock with the bar, two or more sections being arranged end to end on each side of the bar, the end sections being alike and each having one inclined end, and the intermediate sections being alike and having both ends inclined. Each section is also provided with a pair of longitudinally extending rooves on its outer surface to receive proections on the baseof a connector, which connector is held in place by said grooves and by convolutions of the helix wound over said base. These grooves are spaced 90 40 apart, oircumferentially of the covering, so

that the connectors may-be attached at various points around the circumference of thecovering and at any desired point longitudinally thereof. In the accompanying drawing, 7

/Fig. 1 is a side elevation of-a resistor embodymg my improvements, 9. part of the helix being shown in full lines and a part being shown in section;

Fig. 2 is a top plan view of the sup portand a helix.

29, 1926. Serial No. 151,495.

Fig. 4 is a perspective view of one of the end sections of the covering;

Fig. 5 is a top plan view of one of the intermediate sections of the covering; and,

Fig. 6 is an. inverted plan view of the same.

Referring to the drawing, a indicates a flat metal supporting bar, B indicates an insulating covering .on the bar, 0 indicates a helix of resistance metal wound on the covering, and d indicates connectors secured to the covering by the helix. The metal bar is provided with tongues 1, at its ends, constituting stops for locating the insulating covering on the bar. The covering comprises a plurality of sections of insulating material, relatively short with res ect to the length of the bar. The assembl covering shown in Figs. 1 and 2 of the drawin is composed of end sections 6, b, b, an 6, each like the section b in Fig. 4, and intermediate sections 6 and b, each like the section I) in'Figs. 5 and 6. Each end section is semi-cylindrical in cross section, and has a longitudinal groove .2 extending inwardly from its inner face and adapted to fit over the flat bar a. The section has ,a flange 3, at its outer end, and the opposite end of the section is beveled or inclined with respect to the line of the slot 2, as shown at 4. The intermediate sections are also semi-cylindrical in cross section and are longitudinally grooved, as shown at 2, to fit the bar, and both ends of each intermediate section are inclined and parallel with one another, as indicated at 5, in Figs. 5 and 6, the an 1e of incli-..

nation being the same as that of t e inclined ends of the end sections. Each end section and also each intermediate section has parallel grooves 6 on its outer surface, these grooves extending longitudinally of the sec tion and being spaced apart 90 circumferentially of the section.

In assembling a resistor composed of end and intermediate sections, as shown in Figs. 1 and 2, the sections 6 b and b are arranged end to end on one side of the bar, and the sections b, b" and b are arranged end to end on the opposite side of the bar, the bar fitting into the grooves in the sections so ing bar and covering,'the latter being p artly thatthe latter become interlocked with the broken away;

Fig. 3 is a section on the line 3-3 of Fig.1;

bar against rotation thereon. These sections may be suitably cemented to the bar to hold them in place. The helix 0 of resistance wire may then be wound on the insulat volutions of the coil cross the joints between the insulator sections at an angle, throughout the length of the covering.

The connectors d are composed of sheet metal. each having an arcuate base 7, with downwardly turned ends 7, adapted to fit into a pair of adjacent grooves 6 in the covering, and having an upstanding part 7*, to

.which a conductor may be connected. The

grooves 6, being spaced 90 apart about the ody of the covering, the connectors can be placed with the tongues 7 entering two coves in a single section, or grooves in diferent sections, and they may be set at any point along the body of the covering. To hold the connectors to the covering, a few turns of the helix are wound over the base, as clearly shown in Fig. 1.

To make a short resistor, the intermediate sections 6 and b may be omitted, and the end sections will then abut against one another; or to make a long resistor, any desired number of intermediate sections may be added. By the arrangement described, a

ficulty, the same as though the insulator covering were made of a single piece of material. In practice, after the wire has been wound on the covering, it is held in place and its convolutions are kept separate by the application of a suitable cementing compound to the periphery of the resistor, this cementing material being indicated at e.

What I claim is: I

1. A resistor comprising a supporting bar, a. covering of refractory material thereon and a helix of resistance wire wound on the covering, said, covering comprising a. plusection having an end inclined at a greater angle with respect to the longitudinal axis of the bar than the pitch of the convolutions of the helix and abutting againsta like end of another section.

3. A resistor comprising a supporting bar, a cylindrical covering of refractory material thereon and a helix of resistance wire wound on the covering, said covering comprisin two series of relatively short semi-cylindrica sections arranged on opposite sides of the bar and interlocking therewith to prevent rotation thereon, each section having an end inclined .at a greater angle with respect to the .longitudinal axis of the bar than the pitch of the convolutions of the helix and abutting against a like end of another section.

4.-. In a resistor, the combination with a vsupporting bar, of a cylindrical covering of refractory material thereon, said covering cylindrical covering is provided on which; very fine wire may be wound without difcomprising a plurality of relatively short sections each interlocking with the bar to prevent rotation thereon, each section being segmental in cross section and havin an end inclined with respect to the longitudinal axis of the bar and abutting against a like end of another section and each section having longitudinally extending spaced grooves on its periphery, a connector having a base adapted to fit into two of said grooves, and a helix of resistance wire wound on said covering and over said base.

In testimony whereof I hereunto afiix my signature.

GEORGE H. WHITTINGHAM. 

